There have been many boat fenders in the past, both inflatable and resilient, which have been cylindrical and which have eyelets at the top or bottom thereof in order to be suspended from the superstructure of a boat such as a life line, hand rail or any convenient tying-off place. These fenders are usually suspended between a boat and the dock to which the boat is to be tied off and are usually set such that the contact between the dock and the fender is about mid-way up the fender. Note that these fenders are also used between boats which are "rafted" together.
The greatest problem with respect to these types of fenders is that they are not tied off top and bottom, but rather are tied off only at the top. Therefore they tend to pop out or pop up during either rough water conditions, the rise and fall of the tide, or indeed the mere boarding of a boat by persons utilizing the boat.
These fenders in general, are either inflatable or resilient and when pressure is applied by the dock the fender compresses unevenly and deforms so as to squish up and pop out from between the boat and the dock. This of course results in damage in terms of chaffing, rubbing, or even more severe damage, with there being no practical way of keeping the fenders in place when they are lowered over the side of the boat.